Currently, TFT liquid crystal display panels are widely used. In recent years, liquid crystal display panels and organic EL display panels with oxide semiconductor TFTs with a higher mobility than conventional amorphous silicon TFTs are being developed (Patent Document 1, for example).
On the other hand, as liquid crystal display panels become more popular, there is an increasing need for lower prices. Thus, a liquid crystal display panel and a manufacturing method therefor that can reduce the number of photomasks used in photolithography are being developed, for example. Currently, studies are being conducted on reducing the number of photomasks used in a process from five to four or three, for example.
Also, in order to increase the manufacturing yield for TFT liquid crystal display panels, a display panel is proposed in which gate bus lines (also referred to as “scan bus lines”) for supplying scanning signal voltages to the gate electrodes of the TFTs, and source bus lines (also referred to as “data bus lines”) for supplying display signal voltages to the source electrodes of the TFTs are provided on separate substrates (Patent Document 2, for example). Such a structure for the display panel is sometimes referred to as an “opposite matrix structure” or an “opposite source structure”.
FIG. 17(a) shows an equivalent circuit of a conventional liquid crystal display panel 900 having an opposite matrix structure, and FIG. 17(b) is a schematic perspective view of the liquid crystal display panel 900.
The liquid crystal display panel 900 includes a TFT substrate 90A, an opposite substrate 90S, and a liquid crystal layer LC interposed therebetween. The TFT substrate 90A has a substrate 91, and a plurality of pixel electrodes PE formed in a matrix with rows and columns on the liquid crystal layer LC side of the substrate 91. Each pixel electrode PE is connected to the drain electrode of the corresponding TFT, and the source electrode of the TFT is connected to a common wiring line COM. The common wiring lines COM are parallel to gate bus lines GB. The opposite substrate 90S includes a substrate 92, and source bus lines (also referred to as signal wiring lines) SB that are parallel to each other in the column direction, formed on the liquid crystal layer LC side of the substrate 92. It is apparent that the rows and columns are interchangeable, and this is also true for embodiments of the present invention.